Burner apparatus for refining metals



March 30, 1965 G. H. sMrrH ETAL BURNER APPARATUS FOR REFINING METALS`F'iled NOV. 28, 1960 3 Sheets-Shea?l 1 R. J m O r 0 R E T T NHS W a WMAr IQNE. f HD 4 EN mm OY.. EA GR w Y B March 30, 1965 G. H. SMITH ETALBURNER APPARATUS FOR REFINING METALS 3 Sheets-Sheet 2 Filed Nov. 28,1960 INV EN TORS G W N um m mm .W

mm W

w Y B March 30, 1965 s. H. sMrrH ETAL 3,175,617

BURNER APPARATUS FoR REFINING METALS Filed Nov. 28, 1960 I5 Sheets-Sheet3 www@ INVENTORS GEORGE H. SMITH RAYMOND E. ARMSTRONG,JR.

BY Lm 3,175,8l7 BURNER APPARATUS FOR REFINNG NETALS George H. Smith,Berkeley Heights, and Raymond E. Armstrong, lr., Clark, NJ., assignorsto Union Carbide Corporation, a corporation of New York Filed Nov. 28,1960, Ser. No. 72,034 2 Claims. (Cl. 266-34) The present inventionrelates to an improved jet device and process for directing separateflows of a treating fluid and a combustible gas mixture toward thecharge in a metallurgical furnace. It further relates more particularlyto a novel construction and method for cooling such a device whenexposed to the hot molten bath formed therein.

The use of oxygen by the steel industry to speed up production isincreasing every year. Not only are oxygen and other treating gases usedextensively in the final stages of the open hearth method to refine thesteel, but they are used also in the initial stages of the process tospeed up melting of the charges by flame enrichment with oxygen. lt hasalso been found that refining periods may be greatly reduced especiallyin the open hearth type of furnace, by supplementing the normallypresent end positioned burners, with burners which may be suspended fromthe furnace roof thereby permitting heating flames to be directed atclose range upon the upper surface of the furnace charge and on thesubsequently formed molten bath.

In order to fully and most economically utilize the lances which conductthe treating fluids, or direct the heating flames onto the molten bathsurface, it is necessary to provide such lances with adequate means forcountering the effects of high temperatures, furnace atmospheres, andmolten material splash. Generally such lances, or jets as they arefrequently referred to, consist of a plurality of vertically andconcentrically disposed elongated tubes which are so associated as toprovide a flow of the treating material from the lance lower face, whichface is normally spaced Within the range of a few inches to a few feetfrom the bath surface. It is of course necessary to incorporate intosuch devices a cooling system of some sort which most generallyembodies, a passage for conducting a flow of coolant liquid toward thelance face, and a return channel which brings the liquid into contactwith the heated outer casing of the lance. This method of removing heat,by a circulatory coolant flow, is found to be satisfactory up to acertain point after Which it is impossible to achieve a sufficientlyhigh coolant rate of flow to overcome the damages re- :sulting fromexposure to the furnace heat and from rnetal slag buildup on the lanceouter surface due to vfurnace splash.

In the instance of roof burners used in open hearth installations forthe purpose of increasing the scrap melt down rate, the prior art hasproposed devices in which the fuel gas composition is pre-mixed withinsome portion of the burner end thence ignited at the discharge face toform heating flames. A notable disadvantage to this method of flamegeneration is the susceptibility of the combustible mixture to beingignited within the confines of the burner thereby resulting in flashback or burn back of the gas. `Since flashback often results in damageto the burner itself, or parts associated therewith, it is'highlydesirable to prevent such a reaction.

It is therefore a primary object of the present invention to provide anapparatus for treating the charge in a metallurgical furnace, saidapparatus being particularly adapted to resist the detrimental effectsof excessive furnace temperatures and molten splatter.

A further object is to provide a device of the type den l t scribed inwhich a liquid coolant material is provided as a heat transfer mediumfor protecting the surfaces of said device which are exposed to themolten metal bath.

Still another object is to provide a combination oxygen roof jet androof burner of the postmixed gas flame type, including means forprotecting the forward exposed surface thereof with La flow of coolantfluid.

ln the drawing:

FIG. l is a longitudinal View in cross section of a combination oxygenjet and roof burner apparatus embodying the novel features of theinvention;

FIG. 2 is a plan view of the apparatus shown in FIG.

l; and

FIG. 3 is an enlarged cross sectional view illustrating the lowerportion of the apparatus shown in FIG. 1.

FIG. 4 is an enlarged view of the front end discharge face of theapparatus shown in FIG. l.

in brief, the device contemplated by the present invention includes thecombination of a roof lance for introducing flows of a treating gas suchas oxygen to a molten bath, and a roof burner for impinging heatingflames onto the unmeltcd furnace charge and against the bath surface ina single apparatus. The combustion jet, as the device will behereinafter referred to, consists of an inner elongated tube extendingthe burner length, the forward end of said tube being terminated at theburner face in a nozzle portion. A plurality of concentrically disposedtubes surrounding the inner tube, define an nular passages forseparately conducting flows of the treating gas, a fuel gas, and acoolant fluid respectively to the nozzle portion which fixedly positionsthe lower end of said tubes relative to each other. A manifold engagingthe tube upper ends provides a closure thereto and also afford means forcommunicating with the said annular passages. The burner inner tube isprovided at the upper end with means for simultaneously introducing at ahigh pressure, a fuel gas, and a non-combustible, heat vaporizable fluidadditive substance; a deflector interposed at the lower end of saidinner tube deflects the high velocity composite stream of said fuel gasand additive, outwardly toward the burner wall where the latter mayadhere to and flow toward the exposed burner face. The fuel gasthereafter is discharged from the burner face, to mix with an oxygenstream and thence burn as a heating flame.

Referring to FIG. 1, a preferred embodiment of the present combustionjet is shown at 10 and comprises a centrally located inner tube 12, theforward end of which terminates in a discharge opening 14 at the exposedburner face. The upper end of said tube is slideably enclosed by a cap16 which constitutes a removable segment of the manifold 18. Aresiliently sealed opening in said cap 16, including the 0 ring 20retained in a groove therefore, provides a fluid tight connection withthe outer surface of tube 12 in spite of relative movement between thesealing surface of said tube and cap due to thermal expansion Iandcontraction of the respective burner parts in the course of operation.The cap 16 is provided with a port 22 for introducing to the inner tube12 a flow of fuel gas such as methane, or natural gas. According to theinvention, this gas is ordinarily delivered to the inner conduit 12 at asufficiently high pressure to achieve a rate of delivery to the furnaceof about 20,000 to 60,000 cubic feet per hour. Such a volume of gas inpassing through the relatily-small diameter of the inner conduit 12 willof course form a high velocity stream.

lnto the high velocity gas stream thus formed, there is injected arelatively small amount of vaporizable coolant fluid preferably water orsteam, which is introduced through a second port 24 positioned downstream of port 22, so that the injected fluid will be aspirated,substantially atomized, and conveyed as minute droplets in the gasstream toward the burner discharge opening 14. While not presently shownin the drawings, the port 24 may be provided with suitable flow meteringmeans such as a valve, for proportioning the proper amount of liquid orsteam into the gas stream.

The lower or discharge end of tube 12 as previously noted, is generallypositioned in an open hearth or other type furnace, a matter of a fewinches above the molten bath or scrap charge surface and thereforesubject to severe abuse both from the bath heat and from moltensplatter. In addition, as the stream of fuel gas emerges from thedischarge port 14, it will then mix with a stream of oxygen alsoemitting from the burner to form a cornbustible mixture and be ignitedinto an intensly hot flame which tends to further heat the burner face.

Also, since it has been found desirable to introduce the oxygen to amolten bath in the form of a large number of high velocity jets, afurther problem has often been encountered. Since the orifices whichform the high velocity jets are positioned at the lance face, they aresubjected to particular abuse from molten splatter, as are the websections 85 which separate the respective orifices. In order to obtainthe maximum number of oxygen streams, the lateral spacing therebetweenis usually quite limited and consists in many instances of no more thana thin web 85. Since it is quite difficult to adequately cool the websection, burning out at this vital point is one of the most commoncauses for lance failure.

In accordance with the invention, much of the heretofore frequentlyoccuring damage to roof lances of the type described has been overcomeby interposing in the lower end of tube 12, at a point slightly to therear of the discharge opening 14, a fuel stream diffuser element 26.This diffuser in effect separates the tube 12 into respective upper andlower portions. The primary purpose of the deflector is to intercept thedownwardly flowing composite fluid stream and urge said stream laterallytoward the conduit wall. As illustrated in FIG. 3, a preferredembodiment of said element 26 is provided with a generally helicoidconfiguration characterized by gradually sloping surfaces disposed tomeet the high velocity, composite fuel gas and coolant stream, and toredirect said stream into a substantially lateral direction with respectto the burner center axis.

The centrifugal force thereby imparted to the fluid particles making upthe composite stream, will impinge said particles against the smoothinner wall of the conduit 12 at a glancing angle with the result thatthe heavier liquid particles of water will tend to cling to the wallwhile the lighter gas particles will merely be guided into a swirlingpath. When steam is employed in lieu of entrained water, the steam willbe guided into a swirling path along with the fuel gas but since theinner wall surfaces are maintained at a temperature below the condensingpoint of steam, the steam will condense on the wall surfaces formingdroplets of water whereas the fuel gas will leave the jet asaforementioned. During the decarburizing phase of the steelmakingprocess, the use of steam without fuel gas is employed, as the fuel gaswould create a reducing atmosphere. Referring to FIG. 3, an embodimentof the novel deflecting element 26 consists of a screw like memberhaving a peripheral channel 23 formed thereon defined by a spiral land30. This land is provided with an outer diameter approximating theinside diameter of the tube 12 so as to contact the inner wall of saidtube or be contiguous thereto. A smoothly tapered rearwardly projectingportion 32 of the deflector 26, minimizes the actual blocking forceexerted by said member against the rapidly moving composite stream sothat the high forward velocity component of the gas stream will bemaintained along with the swirling component.

The defiector axial length is preferably minimized in order to reduceback drag on the swirling stream and also to permit the formation ofaforwardly advancing thin liquid film on the conduit wall. We have foundthat in a tube having a diameter of about 2 inches, a suitable lengthfor the deflector from forward to rear end would be about 4 inches. Saidmember 26 may be positioned by welding or other suitable means at thedesired location in conduit 12 or it may be adjustably disposed. It hasbeen determined that a high degree of cooling is effected when thedeliector is positioned about 6 inches in from the burner lower face.

As illustrated in the figures, the centrifuging effect on the compositefuel gas stream will cause a thin film of water to form along thecylindrical wall of tube 12 from tne downstream end of deiiector 26 tothe forward opening 14. The high velocity swirling gas stream, togetherwith the gravitational force acting thereon, then will continue to urgethe water film forward along the outwardly (divergent) throat 40 andthence in a lateral direction onto the recessed plane face portion 42 ofthe burner. It has been found that not only does the thin water layercool the exposed burner surfaces by an evaporation pro"- ess, but saidlayer also serves to prevent metallic particles ejected from the bath,from clinging to said surfaces. Actually, there is both a wetting of theexposed surfaces for cooling purposes and also a slight explosive effectwhen the hot bath particles form steam on striking the liquid film. Suchcooling is particularly effective for protecting the previouslymentioned web sections intermediate the oxygen orifices.

Under actual operating conditions, we have found that when the burner isoperated as a heating device, with natural gas as the fuel, a propermixture would constitute 60,000 to 160,000 c.f.h. of oxygen to 30,000 to80,000 c.f.h. of fuel gas, with about l0 to 50 gallons per hour of waterentrained in the fuel stream. In the subsequent refining step where onlyoxygen was introduced to the bath, about 80,000 c.f.h. of oxygen wasinjected while l0 to 70 gallons per hour of water was carried throughthe burner by a nominal ow of fuel gas. When steam rather than water isutilized as the cooling medium, for the abovenoted fuel and coolantmixtures, about 30 to 100 pounds per hour of steam are required.

Again referring to FIGS. 1 and 3 of the drawings the inner tube 12 issurrounded by a second tube 44 outwardly spaced therefrom to define anannular passage 45 for conducting a treating gas such as oxygen towardthe burner forward end. The lower end of said tube engages the burnernozzle in a gas tight seal and the upper end is enclosed by acylindrical ring portion 46 of the manifold 18 to define a annularchamber 48. Said chamber is maintained fluid tight with respect to tube44 and with the adjacent manifold chambers, by resilient seal rings 20,50, and 52 respectively, which are confined in grooves therefor at therespective ends of said ring 46. As noted previously with respect toseal ring 20; the sliding joints so 'formed by the companionate surfacesof the tubes and resilient seal rings, permits a degree of longitudinalexpansion of the burner tubes without the consequence of fluid leakage.t An inlet 54 communicates with chamber 48 for providing oxygen to thelance, and may be coupled to a supply of said gas by a iiexible hose orother suitable form of conduit. The lower end of passage 45 terminatesat the burner nozzle into which a plurality of small bore oxygenorlfices 56 are formed. The oxygen orifices as shown in FIG. 3, aredisposed in circular fashion about the center opening 14 and areslightly outwardly biased from the burner longitudinal axis to formdivergent streams. On emerging at a relatively high velocity from thecircularly spaced orifices the oxygen streams at a point forward of thenozzle face, will impinge against the spiral stream of fuel gas emergingfrom the center discharge opening 14 and thereby provide a combustiblemixture which is immediately ignited to form an elongated conical flame.

It has also been found that, rather than employing the circularly spacedoxygen orifices as presently shown, an annular orifice disposedoutwardly of and substantially concentric with opening 14 will alsoprovide an efficient mixing of oxygen and fuel gas after both of saidgases leave the burner face. The orifices 56 as shown in FIGS. l-3 aredirected in a generally divergent pattern not only for the purpose ofproper mixing with the fuel gas stream but also for accomplishing adispersed treating area on the molten bath surface when the streams ofoxygen are being introduced thereto without a heating flame, as forexample in a deoxidizing step.

In normal furnace operation, the presently disclosed combined roof lanceand burner would first be utilized in a heating capacity by directingOxy-fuel gas flames onto the unmelted scrap metal charge. As the moltenbath is formed, the flow of fuel gas is substantially abated until onlythe oxygen flow is continued. In order to sustain the above mentionedwetting of the exposed lower Wall portion of the center tube, as well asthe exposed burner face, a limited fiow of fuel gas may be providedmerely to act as a carrier for the water additive. It should be notedthough that when `steam rather than water is utilized, the former wouldnot require a carrier and may be introduced alone. Therefore, it ispossible to eect the desired burner protection during all steps of themetal refining process. Especially beneficial in this respect is thedistinct advantage realized that there will be absolutely no mixing ofthe fuel and combustion supporting gases prior to their exiting from theburner. This will of course preclude the possibility of flashback in theburner body or in the gas equipment associated therewith. i

Referring to FIGS. l and 3 of the drawings, the internal cooling systememployed in the present burner consists of a pair of elongatedcylindrical conduits 66 and 62 which are disposed outwardly of tube 44in substantially concentric relationship therewith to define respectivecoolant inlet passage 63 and coolant return passage 64. As illustratedin the figures, said conduits extend substantially the length of theburner and are engaged at the upper end with a circumferential collar 66which forms an integral portion of the manifold .18, The lower end ofconduit 66 terminates at the burner nozzle, at a point rearwardlyadjacent to an annular coolant chamber 67 formed therein. Said chamber67 is provided with a curved forward surface which constitutes the rearwall of the exposed nozzle face 42 such that circulating coolant liquid,which is generally Water, will be received from the water inlet passage63 and then ire-directed into the outer coolant return passage 64.

It has been found that a more efficient cooling of the burner may beachieved by the provision of a baflie member 68 disposed in passage 63,and a similar baffle mem- 'ber 70 positioned in passage 64. Therespective baffles as shown comprise a spiral shaped member which, wheninterposed in the annular coolant passages, urge the coolant stream intoa confined spiral channel. By so doing the velocity of the water isincreased and a smooth fiow is obtained, both of which characteristicsimprove the rate of heat transfer from the burner. These bafiies are Soconstructed and arranged that cooling water passing downwardly throughpassage 63 will be given a swirling motion in, for instance, a clockwisedirection. On passing through the annular chamber 67, the swirlingmotion will be continued and the stream will be thence directed into thechannels formed in passage 64. These latter channels are likewisearranged to continue the stream in a swirling path so as to maintain arapid velocity throughout the lance.

As mentioned above, collar 66 engages the respective upper ends ofconduits 60 and 62, said collar is adapted to threadably engage theoutermost conduit 62 and to slideably, fluid tightly engage conduit 69and tube 44 respectively. A water hose, or similar fiexible conduit notshown on the drawings, but connected to a suitable water d supply, maybe coupled at inlet port 72 to provide a HOW of the coolant liquid to anannular chamber 74 and thence to the coolant inlet passage 63. Likewise,the outer coolant return passage 64 terminates in an annular passage 76which is provided with a port 7S for communication with a second hosefor coolant iiuid.

The nozzle or discharge end of the -burner is provided as shown in FIG.3 with a smooth outer surface which terminates at the forward end in therecessed face 42. It has been found that much of the burner damage,usually caused by blocking of the oxygen orifices with splashed moltenmetal particles, may be avoided by preventing said molten particles fromfiowing down `the burner exposed outer wall and then being aspiratedinto the high velocity gas stream. Iln this respect, a peripheral lip orring 80 formed on said face and spaced radially outwardly of thecircularly disposed orifice 56, permits the down owing molten metal on`the lance outer surface to drip back into the bath.

A circumferential plate 82 fixed to the outer surface of conduit 62immediately below the manifold 18, provides means for supporting theburner in operating position, within a furnace. A metal bail 84 formedto be positioned above cap 22, supportably engages said plate 82.Normally the burner may be transported and positioned in an open hearthfurnace by an overhead traveling crane of the type peculiar to steelmills, which crane is provided with a downward extending hook forengaging the burner bail.

In view of the operating hazards which normally accompany any metalrefining process, it will be readily appreciated that the constructionof the present burner which obviates the necessity for flashbackprecautions is highly desirable. Furthermore, not only is the lance asafe Working tool, but by virtue of the external cooling feature, it hasexhibi-ted a useful life that is prolonged considerably over similarjets or burners utilizing the conventional circulatory cooling means.

Of particular advantage are means by which oxygen may be introduced tothe bath. As suggested by prior art devices, the web portion of thenozzle lbetween oxygen orifices had to be maintained at a certainthickness. The greater this thickness, the less would be the number oforifices which could be formed into any particular lance nozzle. Theunique cooling method presently disclosed permits a greatly reduced webthickness limited only by machining tolerances. Therefore, with agreater number of orices, metal and slag splash is substantally reducedfor a given oxygen flow.

It is understood that the presently disclosed combination treating lanceand roof `burner constitutes a preferrd embodiment of the novelapparatus, and that certain changes and alterations may be made by oneskilled in the art without departing from the spirit and scope of theinvention.

What is claimed is:

l. Apparatus for use in a metallurgical furnace having a forward endadapted to withstand the effects of bath heat and splatter, saidapparatus including an inner conduit for conducting a fiuidized materialcontaining stream consisting of a gas component and a non-gaseouscomponent, an outer conduit spaced from, and extending substantially thelength of the said inner conduit defining an annular passagetherebetween for conducting a second uid, a closure engaging the upperends of said respective inner and outer conduits to position the lowerends thereof approximately adjacent each other thereby defining aforward discharge face, said face having a fiat annular surface with aplurality of orifices therein for the discharge of said second fluid anda large central orifice for the discharge of the components of saidfiuidized stream, defining web sections between said orifices, means forintroducing flows of the fiuidized material and said second fiuid tosaid inner conduit and annular passage respectively, and a defiectordisposed in the lower portion of said inner conduit positionedrearwardly of the forward discharge face, said deector being so arrangedto substantially occupy the cross-sectional area of the inner conduitand to divide said inner conduit into upper and lower portions ofsubstantially constant free and unobstructed cross-sectional areawhereby the uidized stream passing therethrough will be deflected into aspiral stream and the non-gaseous component of said uidized stream willbe impinged against the inner conduit wall forward of said deector andthence be urged along said wall and onto the web sections of said faceby the spiralling gas component of the stream thereby providing anon-gaseous layer on said wall and said forward discharge lface.

2. An elongated jet burner for use in steelmaking to direct a stream offuel gas and a stream of oxygen from the exposed face of said burnertoward a charge of steelmaking materials, said burner comprising anelongated central conduit having upper and lower ends, the lower endterminating in a central discharge opening at the burner forward face,said face having an annular surface with a plurality of orifices thereinand defining web sections between said orices, a second elongatedconduit surrounding said central conduit defining an annular passagetherebetween, means for communicating said annular passage with saidplurality of orifices in said face, means for introducing a pressurizedflow of oxygen into said annular passage for discharge at high velocitythrough said plurality of orifices, means for introducing a pressurizedow of fuel gas into said central conduit for discharge from said centralopening at said burner face, means for entraining water into said fuelgas flow in said central conduit, and a spiral shaped deector positionedwithin said central conduit adjacent its lower end, said deflectordividing said central conduit into upper and lower portions,

.3 said lower portion having a face and unobstructed crossseetional areasubstantially equal to that of said upper portion whereby the water insaid fuel gas will be thrown against and deposited upon the lowerportion wall of said central conduit and thence be urged onto the websections of said face as the fuel gas is discharged ythrough saidcentral opening for admixture with said discharged oxygen.

References Cited in the tile of this patent UNITED STATES PATENTS1,399,006 Cunetry Dec. 6, 1921 1,410,942 Mann Mar. 28, 1922 1,491,318Shearer et al Apr. 22, 1924 1,501,849 Johnson July 15, 1924 1,564,064Hannah Dec. 1, 1925 1,569,163 Waldron Jan. 12, 1926 1,830,574 ThwingNov, 3, 1931 2,446,511 Kerry et al Aug. 3, 1948 `2,454,892 Sprow Nov.30, 1948 2,669,511' Whitney Feb. 16, 1954 2,819,891 Graef Ian. 14, 19582,829,960 Vogt Apr. 8, 1958 2,836,411 Auer May 27, 1958 2,851,351Cuscoleca et al Sept. 9, 1958 2,905,234- Scholz Sept. 22, 1959 2,937,864Kesterton May 24, 1960 3,043,577 Berry July 10, 1962 FOREIGN PATENTS400,793 Great Britain Nov. 2, 1933 542,347 Great Britain I an. 5, 1942559,408 Canada June 24, 1958

1. APPARATUS FOR USE IN A METALLURGICAL FURNACE HAVING A FORWARD ENDADAPTED TO WITHSTAND THE EFFECTS OF BATH HEAT AND SPLATTER, SAIDAPPARATUS INCLUDING AN INNER CONDUIT FOR CONDUCTING A FLUIDIZED MATERIALCONTAINING STREAM CONSISTING OF A GAS COMPONENT AND A NON-GASEOUSCOMPONENT, AN OUTER CONDUIT SPACED FROM, AND EXTENDING SUBSTANTIALLY THELENGTH OF THE SAID INNER CONDUIT DEFINING AN ANNULAR PASSAGETHEREBETWEEN FOR CONDUCTING A SECOND FLUID, A CLOSURE ENGAGING THE UPPERENDS OF SAID RESPECTIVE INNER AND OUTER CONDUITS TO POSITION THE LOWERENDS THEREOF APPROXIMATELY ADJACENT EACH OTHER THEREBY DEFINING AFORWARD DISCHARGE FACE, SAID FACE HAVING A FLAT ANNULAR SURFACE WITH APLURALITY OF ORIFICES THEREIN FOR THE DISCHARGE OF SAID SECOND FLUID ANDA LARGE CENTRAL ORIFICE FOR THE DISCHARGE OF THE COMPONENTS OF SAIDFLUIDIZED STREAM, DEFINING WEB SECTIONS BETWEEN SAID ORIFICES, MEANS FORINTRODUCING FLOWS OF THE FLUIDIZED MATERIAL AND SAID SECOND FLUID TOSAID INNER CONDUIT AND ANNULAR PASSAGE RESPECTIVELY, AND A DEFLECTORDISPOSED IN THE LOWER PORTION OF SAID INNER CONDUIT POSITIONEDREARWARDLY OF THE FORWARD DISCHARGE FACE, SAID DEFLECTOR BEING SOARRANGED TO SUBSTANTIALLY OCCUPY THE CROSS-SECTIONAL AREA OF THE INNERCONDUIT AND TO DIVIDE SAID INNER CONDUIT INTO UPPER AND LOWER PORTIONSTO SUBSTANTIALLY CONSTANT FREE AND UNOBSTRUCTED CROSS-SECTIONAL AREAWHEREBY THE FLUIDIZED STREAM PASSING THERETHROUGH WILL BE DEFLECTED INTOA SPIRAL STREAM AND THE NON-GASEOUS COMPONENT OF SAID FLUIDIZED STREAMWILL BE IMPINGED AGAINST THE INNER CONDUIT WALL FORWARD OF SID DEFLECTORAND THENCE BE URGED ALONG SAID WALL AND ONTO THE WEB SECTIONS OF SAIDFACE BY THE SPIRALLING GAS COMPONENT OF THE STREAM THEREBY PROVIDING ANON-GASEOUS LAYER ON SAID WALL AND SAID FORWARD DISCHARGE FACE.